Bluetooth Low Energy: State 'ServiceDiscovered' is never reached

[Timur Pocheptsov]

@jsulm you need a working run loop under the hood, which is not the case for qeventdispatcher_unix (I am talking about Apple-specific CFRunLoop/NSRunLoop, not sure about Windows, was just guessing)

[Timur Pocheptsov]

@SpaceToon Could you, then, post the code here, to check for some simple errors/mistakes?

[SpaceToon]

@jsulm said in Bluetooth Low Energy: State 'ServiceDiscovered' is never reached:

@SpaceToon

int main(int argc, char* argv[])
{
    QCoreApplication app(argc, argv);

    return app->exec(); // This starts the event loop
}

Yes, I have exactly the same code in my main method.

[Timur Pocheptsov]

@SpaceToon Could you also connect to the server's 'error' signal to check if any error happens?

[SpaceToon]

@Timur-Pocheptsov said in Bluetooth Low Energy: State 'ServiceDiscovered' is never reached:

@SpaceToon Could you also connect to the server's 'error' signal to check if any error happens?

Hello, could you give me a piece of code for doing this? I do not really know how to do so thank you :)

@Timur-Pocheptsov said in Bluetooth Low Energy: State 'ServiceDiscovered' is never reached:

@SpaceToon Could you, then, post the code here, to check for some simple errors/mistakes?

Here is the code. It is just for understanding how BLE works in Qt it is not my final code therefore everything is in one file (there are also header files in which the slots, signals etc. are declared):

/*Uuid of the service from which I want to have the characteristics printed*/
const QBluetoothUuid adafruitServiceUuid = (QUuid("6e400001-b5a3-f393-e0a9-e50e24dcca9e"));

/*Discovering Bluetooth devices*/
void Scanner::startDeviceDiscovery(){

    discoveryAgent = new QBluetoothDeviceDiscoveryAgent(this);
    discoveryAgent->setLowEnergyDiscoveryTimeout(5000);
    connect(discoveryAgent, &QBluetoothDeviceDiscoveryAgent::deviceDiscovered, this, &Scanner::deviceDiscovered);
    connect(discoveryAgent, &QBluetoothDeviceDiscoveryAgent::finished, this, &Scanner::doConnect);

    discoveryAgent->start();
}

/*Prints the name of the device that is discovered*/
void Scanner::deviceDiscovered(const QBluetoothDeviceInfo &device)
{
    qDebug() << "Found new device:" << device.name();
}


void Scanner::doConnect(){

/*All devices are listed in a list. When I see my BLE device, I enter the list element and then */
/*create a connection to this certain ble device*/
    cout << "\nPlease enter the number of your device: ";
    int listNumber;
    cin >> listNumber;

    deviceList = discoveryAgent->discoveredDevices();
    adafruit = &deviceList[listNumber];
    qDebug() << "\nThe element that you chose is: " + adafruit->name();

    controller = QLowEnergyController::createCentral(*adafruit);
    connect(controller, &QLowEnergyController::connected, this, &Scanner::startServiceDiscovery);
    controller->connectToDevice();
}


void Scanner::startServiceDiscovery(){
    connect(controller, &QLowEnergyController::discoveryFinished, this, &Scanner::discoveryFinished);
    controller->discoverServices();
}


void Scanner::discoveryFinished(){
    qDebug() << "\n Service Discovery finished.";
    QList<QBluetoothUuid> serviceList = controller->services();

    QLowEnergyService *uartService = controller->createServiceObject(adafruitServiceUuid, this);

    connect(uartService, &QLowEnergyService::stateChanged, this, &Scanner::printChars);
    uartService->discoverDetails();

}



void Scanner::printChars(QLowEnergyService::ServiceState newState){

    auto service = qobject_cast<QLowEnergyService *>(sender());

    switch(newState){

    case QLowEnergyService::DiscoveringServices:
        qDebug() << "\n Current ServiceState: Dsicovering services";
        break;

    case QLowEnergyService::ServiceDiscovered:
    {

        qDebug() << "Current ServiceState: ServiceDiscovered";

        const QList<QLowEnergyCharacteristic> chars = service->characteristics();
        qDebug()<< "Size in printChars Slot" << chars.size();
        for (const QLowEnergyCharacteristic &ch : chars) {
            qDebug() << &ch;
        }
        break;
    }

    default:
        qDebug()<<"Default";
        break;
    }
}

This is the output:

The connection is successfully created (a blue LED turns on on my BLE device which indicates a succerssfull connection) .

[Timur Pocheptsov]

@SpaceToon I suggest you to create a bug report (please, attach a complete minimal project you are using). In JIRA we can assign it to Denis (who's the author of this back-end), so maybe at least he has an immediate idea of what's wrong. Thanks.

[SpaceToon]

@Timur-Pocheptsov said in Bluetooth Low Energy: State 'ServiceDiscovered' is never reached:

@SpaceToon I suggest you to create a bug report (please, attach a complete minimal project you are using). In JIRA we can assign it to Denis (who's the author of this back-end), so maybe at least he has an immediate idea of what's wrong. Thanks.

Okay, thanks. I created the Bug report here, but I could not assign it to someone.

[harip]

@SpaceToon Is this issue resolved? We are also facing the same issue in Windows 10. As you mentioned, the BLE scanner example is working perfectly fine.

[SpaceToon]

@harip said in Bluetooth Low Energy: State 'ServiceDiscovered' is never reached:

@SpaceToon Is this issue resolved? We are also facing the same issue in Windows 10. As you mentioned, the BLE scanner example is working perfectly fine.

Hey,
not it is not fixed yet, but a developer is investigating the issue. You can track the current status of the bug here in Jira.

[Dihambo]

The QTBluetooth Central API is not supported on any platform.
see the first table in Qt Bluetooth